Article 01-23-1 is being republished in its entirety to update the model years and to update the Service Procedure to replace the Low Flow Injectors and not the Compuvalve assembly.

ISSUE:

Due to possible regional Fuel Quality issues in some areas, it may be necessary to clean the low flow injectors in the Compuvalve, and the associated fuel introduction hardware between the Compuvalve and intake manifold (fuel rails, injector sleeves). Typical symptoms of contamination in the low flow injectors are:

Rough run in Alt fuel mode most noticeable at idle, runs OK in gasoline mode

No start (green light on) when vehicle is cold in Alt fuel mode, but will start if vehicle has been previously warmed up in gasoline mode

No start in Alt fuel mode (with green light on) at any time, but starts in gasoline mode.

ACTION:

Verify condition. If normal diagnostics cannot pinpoint the condition, clean the Low Flow CNG injectors in the Compuvalve. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

NOTE:

THIS SERVICE PROCEDURE SHOULD ONLY BE PERFORMED BY AN AUTHORIZED CNG FUEL SYSTEM TECHNICIAN.

NOTE:

FOLLOW ALL CNG FUEL SYSTEM SAFETY PROCEDURES LISTED IN THE APPROPRIATE WORKSHOP MANUAL.

Set fuel selector switch to Alt position.

If the vehicle cannot be started in Alt fuel mode, the low flow injectors may be completely stuck closed. If this is the case, attempt to free them by applying 12 Volts directly to the injector coil:

Disconnect the low flow injector harness (J14).

Apply battery voltage to pins A and D (marked on the side of the connector) to open injector #1. Listen for an audible click to confirm that the injector has opened.

NOTE:

THE INJECTORS ARE NOT DESIGNED TO HAVE A CONTINUOUS 12 V SUPPLY (NORMAL OPERATION IS ABOUT 1.5 V). PROLONGED EXPOSURE TO 12 V WILL CAUSE PERMANENT DAMAGE, SO LIMIT THE 12 VOLTS TO A MAXIMUM OF 5 SECONDS.

If no click is heard, try several more times, always for 5 seconds or less (wait at least 5 seconds between application of voltage).

Repeat the above step for injector #2 applying voltage to pins B and D. If vehicle can be started continue to Step 3.

If the vehicle can still not be started after this procedure, replace the Low Flow Injector assembly.

Leak check only the connections removed.

Restart engine, verify the problem has been corrected. Return vehicle.

Start and run engine to a minimum temperature of 75° C (165° F) (MST or ECT depending on vehicle model year) to ensure engine stability.

Shut off AC and Defrost.

Disconnect the electrical connection to the CNG tank valve and run the engine until it auto switches to gasoline.

Following procedure in GFI Service Manual, bleed off residual CNG line pressure.

Remove coalescent filter body and drain any contaminants. Wipe the inside with a clean cloth.

Fill to within 1/4 inch of the top with isopropyl alcohol with coalescent filter in place (alcohol must be at least 90% by volume).